The present invention is in the field of wiring and wire patterns.
This invention relates to methods and apparatus useful in the electronics and automotive industries. More specifically, this invention relates to the testing of heater wiring useful in automotive applications.
A printed conductive pattern is commonly printed on the rear window (backlite) of an automobile for purposes of defogging and deicing. Often, a silver paste is silk-screened onto a glass substrate and heated to form a pattern of silver fret lines. Similar conductive patterns may also be constructed of actual wires imbedded in or attached to the automotive glass. Such patterns have also been used on the front window of automobiles for deicing the windshield wiper rest position. Other applications of such patterns include antenna applications of various types. The automotive glass may be acquired commercially with the conductive pattern already provided.
Generally, a two-dimensional drawing of a glass window is produced. A conductor pattern drawing is then produced based on given specifications, such as conductor width, distance between conductors, etc. A peeling film is then cut along an outline of the conductor pattern to produce a cut mask, in which the conductor portion remains uncut. The cut mask is adhered to a screen on which a photosensitive material is applied. The resultant cut mask is exposed and washed with water to prepare a print screen, in which a conductor portion corresponds to an opening. The screen overlaps the glass plate to print the conductive paste.
The width of each conductor is typically 1 mm or less so as not to interfere with the field of view of a person operating the vehicle. In addition, the lengths of heater wires may be different from one another, so that the widths of respective conductors may change to control the resistances of the wires. In order to differentiate the heating of a central, high-temperature area from that of a peripheral, low-temperature area, the width of an individual heater wire may be modified over different portions of the heating area.
For this reason, drawing of a conductor pattern and preparation of a cut mask are performed by extremely sophisticated and precise manual operations. Still, it is difficult to maintain consistent thickness and continuity throughout the entire wiring pattern while varying width from wire to wire, and while also varying the width along each individual wire.
As the complexity of these patterns increases, testing becomes more difficult and expensive. For example, interconnecting lines are often used along with the traditional heating lines to allow use of a backlite grid as an antenna as well as a heater grid. Unfortunately, these interconnecting lines make the detection of broken heating lines more difficult, as electrical current may now flow around the broken part and heat the remainder of the heating line.
It is also desirous to minimize the amount of time required to test each conductive pattern, as automotive parts such as backlites are manufactured at a known rapid rate. A typical automotive window glass manufacturing system requires a complete operation in 20 seconds or less.
It is therefore an object of the present invention to develop a system and apparatus for quickly, inexpensively, and accurately testing the performance of such a conductive pattern.
Although described with respect to the field of automotive vehicle components, it will be appreciated that similar advantages of quick and accurate testing may obtain in other applications of the present invention. Such advantages may become apparent to one of ordinary skill in the art in light of the present disclosure or through practice of the invention. For example, this invention may have applications in other situations where heated regions of any other type of material need to be tested.
The present invention includes testing devices and testing systems. This invention also includes machines or electronic apparatus using these aspects of the invention. The present invention may also be used to upgrade, repair or retrofit existing machines or electronic devices or instruments of these types, using methods and components used in the art. The present invention also includes methods and processes for using these devices and systems.
The testing system of the present invention comprises an article of manufacture, such as an automotive windshield or backlite, having a conductive pattern placed on its surface or embedded within. An electrical power source is placed in contact with the conductive pattern, whereby electrical current may be circulated throughout at least a portion of the pattern. An infrared detection device, such as an infrared camera, is positioned sufficiently near the article of manufacture, and is adapted to collect data from the selected portion of the conductive pattern. A data collection device in communication with the infrared detection device is then adapted to receive the infrared data from the detection device.
The conductive pattern may comprise a printed conductor, such as silver or copper fret, or may comprise actual wire embedded in the article of manufacture.
The data collection device may be any appropriate device, such as a computer adapted to collect data from the infrared detection device, process the data, and determine the performance of at least a portion of the conductive pattern. The performance determined may include any appropriate characteristic, such as continuity, uniformity, or homogeneity. The data collection device may then send a signal or instructions to robotic actuators or other industrial apparatus, whereby parts that do not meet predetermined performance criteria may be removed from the assembly line. The data collection device may alternatively send performance data for each part to a data storage apparatus for later retrieval and analysis.
Also included in the present invention is a method of testing a conductive pattern. In the method, a first set of infrared data is collected from at least a portion of a conductive pattern. Electrical current is then circulated throughout that portion of the conductive pattern. A second set of infrared data is then collected from the portion. The first set of infrared data is then subtracted from the second set of infrared data, whereby any effects of pre-existing thermal nonuniformities may be removed. The performance of at least that portion of the conductive pattern may then be determined. The performance determined may include any appropriate characteristic, such as continuity, uniformity, and homogeneity. This method may also include autonomous decision making, based upon pre-determined criteria and thresholds, and the providing of instructions to industrial equipment such as microprocessors and robotic actuators, as known and used in the art.
The present invention also includes a system for determining the thermal performance of such a conductive pattern. The system utilizes thermal detector, such as an infrared camera or other infrared detection device known in the art. The thermal detector is preferably adapted to generate first and second data sets comprising infrared data of the conductive pattern. The data sets may be captured while different external currents are applied to the conductive pattern. In a preferred embodiment, the first data set is captured with no external current applied to the conductive pattern, while the second data set is captured with the conductive pattern having an external voltage applied for a time sufficient to appropriately heat the conductive pattern. The data sets may comprise image data captured by an infrared camera and stored in a temporary data buffer.
The system also utilizes a microprocessor. The microprocessor has processing instructions for comparing the first and second data sets, whereby preexisting thermal effects or conditions may be removed from the second data set. The microprocessor may then determine the performance of the conductive pattern using the results of the comparison between data sets. The microprocessor may then report the performance results. This reporting may be any signal or transfer of data made to a data storage unit, industrial machinery, or display apparatus known in the art.
A preexisting data set may also be stored in the system or data storage device, the preexisting data set preferably containing information pertaining to the conductive pattern. This information may include pattern coordinates, performance criterion, and preferred thermal profiles. The values of these parameters may vary depending upon the part or conductive pattern being tested. In a typical industrial application, one testing apparatus may be used to test several different parts, such as windshields for several models of automobile. This preexisting data may then also be compared by the microprocessor to the second data set.
The microprocessor may also contain instructions for generating a thermal profile for the second data set. The determination of performance may then be determined based upon the thermal profile, such as by applying thermal criterion or thresholds to the profile.
Also included in the present invention is a manufacturing system for testing articles of manufacture comprising conductive patterns. The manufacturing system preferably comprises a conveyance device that is adapted to convey the articles of manufacture. This may include any appropriate conveyance device known in the art, such as a conveyor belt or assembly line. The system also preferably includes a station along the conveyance device for testing the articles of manufacture. This station preferably comprises an electrical power source that may be brought in contact with the conductive pattern, whereby electrical current may be circulated throughout at least a portion of the pattern. The station preferably also comprises an infrared imaging device. The infrared imaging device, such as an infrared camera or infrared sensor, is preferably adapted to collect image data from at least a portion of the conductive pattern. The station preferably also includes a computer adapted to collect the image data from the infrared imaging device, process the image data, determine the performance of at least a portion of the conductive pattern, and report the results of the performance.
The manufacturing system may also comprise a robotic actuator adapted to receive the results from the computer. The robotic actuator may be adapted to remove from the conveyance device any articles of manufacture failing the performance determination. The actuator may also be adapted to move any such article of manufacture onto a second conveyance device.
The manufacturing system may also comprise a marking device, the marking device adapted to mark certain articles of manufacture based upon the determination of performance. The manufacturing system may additionally comprise a data storage device adapted to receive and store data pertaining to the determination of performance. This data may be stored temporarily, and may be adapted to be retrieved upon command. The manufacturing system may also comprise a display device, such as a monitor or series of LED""s, adapted to receive and display data pertaining to the determination of performance.